The present invention relates to direction finding systems and, more particularly, to an adcock DF-on-the-fly type direction finding system employing a beam forming dispersive delay line.
Direction finding (DF) systems are well-known in the art and are typically employed to find the source of a radio frequency (RF) transmitter. For example, radio transmissions from enemy aircraft or vessels can be used to determine their presence and location while they are still beyond the limits of radar detection. RF responsive DF systems can also be used to pick out an individual member of a group detected by radar such as in the case of quickly locating a particular private plane within an airport's landing pattern.
Typically in such systems, an array of receiving elements is deployed in a known configuration so as to develop a plurality of respective electrical output signals as a result of receiving the RF signal of interest. These electrical signals are then processed to determine the angle of arrival of the RF signal that caused them. Such a system employing a linear array and surface accoustic wave (SAW) device for time compressing the signals from the elements of the array is shown in U.S. Pat. No. 4,245,333 to Jelks. In a so-called adcock DF-on-the-fly system, a square array of four elements is employed.
Other patents of relevance and interest to the subject matter of the present invention include U.S. Pat. No. 4,229,740 to Krilanovich; U.S. Pat. No. 3,946,388 to Schifrine; and U.S. Pat. No. 3,631,496 to Fink et al.
Typical prior art adcock DF systems are complex, costly, and have many sources of potential error such as temperature sensitivity induced phase and amplitude errors within the state-of-the-art components employed therein to reduce size as much as possible. A typical example is the SAW device of the above-referenced Jelks patent. A three dispersive line phasing system uses costly quartz lines which have poor sidelobe performance. A four dispersive line amplitude system requires the purchase of four matched lines.
Wherefore, it is the object of the present invention to provide a DF system with a reduction in components, simplification of octantal error reduction over a wide band, which reduces temperature induced variations in DF accuracy, and which reduces size and power consumption of apparatus.
It is a further object of the present invention to provide a DF system using a specially designed beam forming dispersive delay line to provide pulse compression and direction vectors from a single device, thus providing DF information on a large number of simultaneous signals over a wide band of frequencies.
It is another object to provide a more compact adcock DF-on-the-fly system in which the pulse compression process and signal direction vectors are generated in a single device.
It is also an object to provide a substantial reduction in the required number of components in a DF-on-the-fly system, particularly in the number of pulse-compression delay lines which constitute an expensive component.
Additional objects are to provide a reduction in the number of phase tracking signal channels to two and to provide a simplified means of controlling octantal error over a wide band.